108 Volts DC shock from Zero plate

[andym]

I have a PRS Alpha that I purchased in late 2008.
It has been running fine but today I got a 50hz buzz from the zero plate when I held it and put my other hand on the X Axis rail which is grounded.
Because of this I got my volt meter and put one probe on the plate and the other on the X Rail and got a reading of 108 Volts DC.....
Is this normal? I then opened the control box and test the output connectors on the control board and found all of the outputs that the zero plate is connected to gave the same result.

Just so you know I'm in the UK and have a 240v AC supply to the control box in addition to the 3 phase for the spindle.

Any ideas?

[Burkhardt]

You may have lost the internal ground connection of your electronics box. Check the continuity of the internal ground to mains ground. That should fix it. The buzz is rather normal without that due to filtering capacitors in the power supply that let some (usually harmless) AC through.

[paul_z]

There is another, dangerous possibility. You might have one of the "hot" 3 phase leads hooked to ground. Unless you are certain that you know what you are doing, call an electrician.